Rotary undercutting tool



June 2, 1959 E. KUSTUSCH 2,888,968

ROTARY UNDERCUTTING TOOL Filed Aug. 5, 1957 2 Sheets-Sheet 1 IN VEN TOR. EbMUA D KMSTl/SC/l June 2, 1959 E. KUSTUSCH ROTARY UNDERCUTTING TOOL 2 Sheets-Sheet 2 Filed Aug. 5, 1957 INVENTOR. 'onu/vo n1: ruscf/ 24 M 4 rraxn/gy United States Patent ROTARY UNDERCUTTING TOOL Edmund Kustusch, Detroit, Mich. Application August 5, 1957, Serial No. 676,353 4 Claims. (Cl. 145-1145) The object of my invention is to provide a tool capable of undercutting the peripheral portion of a circular socket adapted to receive the head of a screw. The result of the operation of the tool is a radially-recessed groove 1n the wall of the socket at a level below the top surface of the object in which the socket is located. A groove of this type is needed for insertion of a member which fits over the top of the screw and extends into said groove for an interlocking engagement therewith to prevent longitudinal movement of the screw out of the socket.

A more specific object of the invention is to provide a tool in which a cutting element will not operate until it has been lowered to a predetermined depth in said socket and in which the cutting element will be automatically withdrawn from its operative position when withdrawn from said depth. The last-named feature is essential to prevent damage or destruction of the marginal portion of the socket which overhangs said annular groove.

I shall now describe my tool with reference to the accompanying drawings in which:

Fig. l is a vertical sectional view of the tool, the view including an outer jacket and disclosing the cutting blade of the tool in its operative position;

Fig. 2 is a side elevational view of the tool without its jacket;

Fig. 3 is a side elevational view of a blade-guiding element within the lower portion of said tool;

Fig. 4 is a sectional view on line 44 of Fig. 1;

Fig. 5 is a sectional view on line 5-5 of Fig. 1;

Fig. 6 is a vertical sectional view of a bar provided with a socket, for reception of the head of a screw, the View disclosing an annular groove within the socket below the upper surface of the bar as formed by the cutting blade of the tool;

Figs. 7 and 8 each show a vertical sectional view of the tool in consecutive stages of its application to a socket.

Similar numerals refer to similar parts throughout the several views.

The tool includes a cylindrical housing 10 which is open at both ends and which, midway its length, is provided with an annular external head 11. The lower end portion of the housing is expanded radially from an internal shoulder 12 downwardly. The housing fits axially, from above, into a cylindrical jacket 13, the internal diameter of its upper portion being such that the jacket fits slidingly about the bead 11, said portion terminating with an interior shoulder 14 (Fig. 7). It will be noted that the above-described structures of the casing and the jacket leave a free space about the casing from said bead 11 to said shoulder 14. Disposed in said space is a spring 15 which is coiled about the casing, bearing at one end against said head 11 and at the other end against said shoulder 14.

At the top, the jacket is provided with a retaining ring 16 which is screwed upon the threaded upper portion of the jacket to prevent displacement thereof, the ring including a flange 16a which is adapted to bear from above against said bead 11. The interior of the lower portion of the jacket, beginning from said shoulder 14,- is in a sliding contact with the wall of the housing, but extends beyond the lower end thereof and is formed into a cylindrical skirt 17 of a reduced diameter, the skirt being open at said lower end.

Telescopically disposed in the upper portion of the housing is a hollow spindle 18, which at its upper portion 20, is provided with two diametrically opposed slots 19 extending vertically. Said portion 20* of the spindle is reduced in diameter and threaded internally, as shown at 21. As the lower portion of the spindle is of an expanded diameter, the structure results in the formation of a shoulder 21a (Fig. 1).

Located axially within the upper end of the housing and extending into the spindle 18 is a shaft generally identified by numeral 22. It comprises a cylindrical plug 23 seated within the upper end of the housing and provided with a flange 24 abutting from above against the top of the wall of the housing, and an axially-disposed shank 22a extending upwardly from the plug. The plug is provided with a radial bore 25 containing a coiled spring 26 hearing from inside against a ball 27 which fits into an annular groove 28 in the inner surface of the wall of the housing.

Said shaft 22 forms a unit with said housing with which it is adapted to be moved downwardly with respect to the jacket 13 so that said housing with said shaft may be considered to be a plunger. A length 22b of said shaft 22, extending downwardly from the plug is of a diameter to fit telescopically into the spindle 18. It is this length that is provided with a diametrical bore 29. Located in the bore is a pin 30 which at each end projects into a respective slot 19 in said spindle. Below said pin, said shaft 22 includes a slender stem 31, the portion of the shaft at the upper end of the stem defining a shoulder 32. Coiled about the stem 31 is a spring 33 which, bearing at one end against said shoulder 32, bears at the other or lower end against the upper end of the mid-portion 20 of the vertically-movable spindle 19 and keeps it normally at what will be called its low position.

Interposed between the housing 10, and the lower portion of the spindle is a bushing 34 which at its upper end bears against the shoulder 12 of the housing 10.

Threaded into the internally threaded mi'dportion 20 of the spindle 18 is the upper end 36 of a pilot 37 which is a cylindrical member terminating at the lower end with a tip 38 of a reduced diameter. The pilot, best shown in Fig. 3, contains an axial bore 39 extending from the top to a point adjoining said tip, and a short bore 39a of a reduced diameter which extends downwardly into the tip. In addition, the pilot contains a diametrical slot 40 extending from the top to the lower end of the bore 39. Located with the pilot at the bottom of the bore 39 is a steel ball 41.

Disposed within the slot 40 is a flat blade 42, which, by reason of a slot 43 longitudinally extending therein, has the shape of a bifurcated member including two legs 44 resiliently opposed to each other. At the lower end the opposed legs straddle the ball 41. The end portions 45 of said legs diverge from each other in an inverted V-formation, the ball 41 fitting into the gap between said end portions, the outer edges 46 of said portion 45 being set obliquely to the axis of the pilot and being the cutting edges of the blade.

The drawing in Fig. 6 shows a bar 50 in which a threaded bore 51 contains a screw 52 including a head 53 seated in a socket 54. At the top, the socket is ex-- panded radially by an annular groove 55 which is cut 3 into the wall of the socket so as to leave an overhanging lip 56.

It will be understood that for operation, the shank 22a is to be secured within a chuck of a machine in which said chuck will be rotated about its axis. Thus the whole tool, including the shank 22a, the housing 10, the elements contained in the jacket 13 and the jacket itself, may be rotated as a unit, in the manner of a dn'llin a drill press. However, it must be stated here that the tool is also adapted for manual operation. By this I mean that the tool may be operated by means of a manually operated device such as is used for the operation of a hand drill.

At this point it may be stated that, normally, when the tool is in its inoperative condition, the lower end of the skirt 17 of the jacket 13 is at a level spaced from the lower end of the blade 42 as shown in Fig. 7 and that the tips 57 of the cutting elements 45 are contained within the slot 40 of the pilot.

In the initial stage of its application to a socket in which an annular groove is to be cut, the tool is shown in Fig. 7 It will be noted that at this stage the tip 38 of the pilot 37 is located within the socket at the top of the vertical bore 51a in plate 50a, but that the lower end of the skirt 17 of the jacket 13 is in a spaced relation to the upper surface of said plate.

In the next or second step of the application of the tool, said tool is pressed downwardly, as a result of which the pilot 37 bearing from below against the shoulder Zlla of the spindle 18 will move the spindle upwardly against the tension of spring 33 till the lower end of the skirt 17 will bear from above against the top surface of plate Sfia, as shown in Fig. 8. As the skirt will touch said surface, the rotation of the jacket 13, of which the skirt is a part, will be slowed or stopped entirely by the fractional contact with said surface, while the housing 10, with all the elements contained therein, including the cutting blade, will continue rotating within said jacket. It is to be noted that at this stage the bottom of the blade 42 is still slightly above the top surface of said plate Sila.

Now, as the third step, while pressure on top of the tool is continued, the housing 10, with the plunger 22, is forced downwardly against the resistance of spring 15 till the lower end of the stem 31 of the plunger is brought to bear against the upper end of blade 42,, as shown in Fig. l. 7

As the stern presses the blade downwardly, the cutting elements 45 straddling the ball 41 are spread apart by said ball so that the cutting edges 46 of said elements will project outwardly from the slot 40 in the pilot 37. It is in this position of said cutting elements, during the rotation of the spindle about its axis, that they will carve out an annular groove 55 in the socket 54, but will leave an overhanging lip 56 best shown in Fig. 6.

Once the groove has been formed, the tool may be removed from its operative position within said socket. It will be obvious that this must be done in such a manner that the cutting elements 45 will not cut into the lip. This'would be sure to happen if during the withdrawal of the tool from the socket, the cutting elementsof the tools were still in positions outwardly extending from the slot in the pilot. However, the retraction of the cutting elements from their operative positions is effected automatically. As the downward pressure upon the tool, preliminary to its withdrawal from the socket, is released, it is first the stem 31 which is disengaged from its contact with the end of the blade 42. Relieved of pressure from above, the two legs of the blade draw towards each other by virtue of their own resiliency. As a result, the inner edge of the cutting elements 45, bearing against the ball, are drawn towards each other, the whole blade shifts upwardly and the tips 57 of said cutting elements 45 are retracted into the slot 40 in the pilot, thus eliminating the danger of cutting or damaging the lip 56. Following this, spring 33, bearing against the midportion 20 of the spindle 18, returns said spindle 18 with the blade 42 to its normal position with relation to the lower end of the skirt 17, as shown in Fig. 7.

What I wish to claim is as follows:

1. A rotary cutting tool comprising a vertical cylindrical casing, a hollow cylindrical spindle axially fitting into the casing for an axial sliding movement therein, the wall of the spindle being provided with two diametricallyopposed vertical slots, a shaft axially disposed within the casing, the shaft including a plug axially secured within the upper end of the casing, an axial shank extending up wardly from the plug for engagement with means adapted to impart a rotary movement to the tool about its axis, and a stem forming a part of the shaft and axially fitting into the spindle, a pin held diametrically within the shank above said stem, the ends of the pin projecting into the respective slots in the wall of said spindle for a vertical sliding relation therewith, a cylindrical pilot disposed within the lower end of the spindle and connected thereto for rotation therewith, the pilot having a solid lower tip but being provided with an axial bore and with a diametrical slot, both extending from the top of the pilot to said lower tip, a ball seated within the lower end of the bore, a fiat blade slidingly disposed within the slot, the blade being bifurcated by a longitudinal slot therein and including, at the lower end, two cutting elements each having a slanting inner edge bearing from one side against the ball and an outer, substantially parallel cut ting edge, the cutting edges being normal 1y contained within the slot in the pilot, spring means acting from below against the spindle to keep the top of the blade in a normally spaced relation to the lower end of the stem, the stem being adapted to be brought against the tension of the spring into a downwardly-pressing engagement with the upper end of the blade to cause the cutting elements to be spread apart by the ball and to extend outwardly of the slot within the pilot for a cutting operation during the rotary movement of the casing.

2. A rotary cutting tool including a cylindrical casing open at one end and'containing at the other end anaxial plug, a shank extending outwardly from said plug for connection to means adapted to rotate the tool about its axis, a stem axially extending from the plug into the. casing, a hollow, longitudinally slidable spindle disposed within the open end portion of the casing for rotation therewith the cylindrical spindle having in its wall two vertical, diametrically-opposed slots, a pin held diametrically within the stem, one end of the pin projecting into one of the slots and the other end of the pin projecting into the other slot, spring means normally urging the spindle towards said plug, a cylindrical pilot located within the spindle and secured thereto for rotation therewith, the pilot having a tip of a restricted diameter and being provided with an axial bore and a diametrical slot, both extending from its upper end to the line 0i junction with said tip, a ball within the bore at said junction, a bifurcated flat blade within the slot of the pilot, the blade having two opposed legs disposed in the same plane, each of the legs terminating with a cutting element having a slanting inner edge bearing against said ball and an outer cutting edge, the ball fitting between said cutting elements, the spindle being adapted to be pushed telescopically into the casing against the tension of said spring means to cause the stem to bear against the blade from the end remotefrom said cutting elements to spread said elements, by means of said ball, into operative cutting position during the rotation of the casing. H

3. A rotary tool adapted for operation in. a screw socket in a stationary object, the tool including a cylindrical casing open at the lower end, but closed at the upper end and provided at said upper end with a shank for connection to means adapted to rotate the casing about its axis, a stem axially extending into the casing from the upper end thereof, a hollow, longitudinally slidable "spindle in the form of a cylinder disposed within the lower portion of the casing for rotation therewith the wall of the casing having two vertical, diametrically-opposed slots, a transverse pin held in the stem and having its ends projecting into the respective slots, a cylindrical pilot axially held within the spindle for rotation therewith, the pilot being provided with a diametric slot extending from its top downwardly, and terminating at the lower end with a diametrically reduced tip, an oblong blade disposed in the slot, the blade terminating at the lower end with two, resiliently opposed cutting elements, a stationary member wedged between said cutting elements, spring means within the spindle to keep the upper end of the blade and the lower end of the stem in a normally spaced relation to each other, the stem being adapted to be brought to bear against the upper end of the blade to cause the elements to be spread by the stationary member wedged therebetween, a jacket enclosing the lower portion of the casing, spring means to keep the jacket in a yielding telescopic relation thereto, the lower end of the jacket being adapted to bear against the rim portion of the socket under suflicient pressure upon the casing from above, to overcome the tension of said last named spring means.

4. A rotary tool adapted for operation in a screw socket, the tool including a vertical cylindrical jacket, a cylindrical casing, the lower end of which fits telescopically into said jacket, spring means coiled about the casing, the casing being adapted to be depressed axially into the jacket against the tension of the spring, the lower end of the jacket being at all times at a lower level than the lower end of the casing, the casing being open at the lower end and having at the upper end an axially-disposed shank for connection to means adapted to rotate the casing about its axis, a stationary stem axially extending into the casing from said last-named end, a hollow, longitudinally slidable spindle in the form of a cylinder disposed within the open end portion of the casing for rotation therewith, the wall of the spindle having two diametri- Cally-opposed vertical slots, a pin held diametrically in the stem, the ends of the pin being in vertical sliding engagement with the slots of the spindle, spring means normally holding the spindle in an outwardly-extending position from within the casing, a cylindrical pilot located within the spindle, the pilot having a tip of a diameter to fit into the socket and being provided with an axial bore and a diametrical slot, both extending from its upper end to the line of junction with said tip, a ball within the bore at said junction, a bifurcated flat blade within the slot of the pilot, the blade having two opposed legs disposed in the same plane, each of the legs terminating with a cutting element having a slanting inner edge bearing against said ball and an outer cutting edge, the ball fitting between said cutting elements, the spindle being adapted to be pushed telescopically into the casing against the tension of said spring means to cause the stem to bear against the blade from the end remote from said cutting elements to spread said elements, by means of said ball, into operative cutting position during the rotation of the casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,013,970 Thompson Jan. 9, 1912 1,386,249 Gander Aug. 2, 1921 2,234,477 Marshall Mar. 11, 1941 2,401,074 Huelster May 28, 1946 FOREIGN PATENTS 443,679 France July 20, 1912 

